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Geological Sciences

Biostratigraphy

Biostratigraphy

Biostratigraphic services include micropaleontology (foraminifera), calcareous nanoplankton, palynology, palynofacies, wellsite biostratigraphy, stratigraphic reviews, correlation studies and multi-disciplinary integrated studies. Core Laboratories is increasingly involved in high-resolution biostratigraphy and palynofacies/biofacies studies fully integrated with seismic, wireline log and sedimentological or lithofacies data. The resulting sequence stratigraphic interpretation gives a much fuller geological understanding of the sedimentary section than that provided by biostratigraphy alone.


Foraminferal and Calcareous Nannoplankton Analyses
It is important to date a micropalaeontological assemblage in terms of standard biozones and necessary to recognise stratigraphically significant rock units based on their micropalaeontological assemblage for interwell correlation. Micropalaeontological and palynological assemblages can also be used to assess the depositional environment since different microfauna are found associated with different water depths. This data is valuable for geological and reservoir modeling since the depositional environment dictates the likely sand geometry, continuity and reservoir quality. Similarly in carbonate environments the recognition of fore reef, back reef, or lagoonal facies is important for predicting the most likely location for the reef.

Semi-quantitative analysis refers to visually estimated abundances and is recommended for basic interpretation of age and depositional environment. Quantitative analysis provides absolute counts and is particularly useful for detailed, high resolution biostratigraphic studies in a sequence stratigraphic framework.


Palynofacies Analysis
Detailed palynofacies determination can be of great value for correlation and assist in defining sequence stratigraphic events by putting the relatively few taxonomically based palynological marker events in the correct stratigraphic context.Palynofacies analysis allows the identification of distinct palynosequences bounded by "key" stratal surfaces of regional and/or local sequence stratigraphic significance. Correlatable stratal surfaces often prove to be coincident with (and enable more accurate picking of) seismic events in well sections. Stratal surfaces recognised from palynofacies associations have been proven to form an invaluable framework within which each palynology event can be seen in its geological context. All this can be achieved independently of, for example, lithofacies, electrofacies and sedimentology. If, however, palynofacies is integrated with other disciplines its effectiveness can be considerably enhanced.


Biostratigraphy

Wellsite Biostratigraphy
Both micropaleontological and palynological analyses can be performed at the wellsite in self-contained units both on and offshore. The data gathered can be invaluable for quick evaluation of age and environment of the formations drilled. Wellsite data may also be useful for biosteering in horizontal wells where vertical variations in palynomorph character allows real-time adjustment to bit trajectory to keep the well on target.